Windows Security, Logon To POP.EAST.COX.NET

Bought a Toshiba laptop 10 months ago and everything worked fine. With MS updates (only downloaded defender and Vista related items) things started to happen. Have worked through every problem except can not recieve emails. (Can send with no problem.) Have Cox internet and they determined I can recieve emails through their website so it is Vista interference. Spent two hours yesterday with Toshiba tech service trying to isolate and repair problem. Was not successful.

The problem is this: When Windows mail comes up, or when I hit send and receive, I get a box that says "Windows Security, Logon to POP.EAST.COX.NET" and the appropraite places to put in my Username and Password. When this is done, It just comes back with the same Windows Security box. The Toshiba Rep tried numerous things with accounts and the usual settings, changing passwords, setting up a new account and trying to use that and all resulted in the same "Windows Security" box. He feels that there is something in Windows Security that is out of whack and said to try to delete that program but could not find it to delete it. (I have router so no firewall is not a problem and AVG antivirus.)